The self-assembling process in articular cartilage is emerging as a potentially robust approach for engineering large and small cartilage constructs. The objective of this proposal is to evaluate self-assembled articular cartilage in resurfacing the patella by quantifying the biologic response (i.e., host response to the construct), dose response (i.e., identifying the minimum number of necessary cells), and durability (i.e., stability, integriy, and maturation over a year), as defined by the FDA. Statistical optimization to improve the functionality of self- assembled cartilage constructs has yielded a powerful combination of externally applied stimuli that result in constructs with biomechanical and biochemical properties on par with those of native cartilage. Among a multitude of helpful stimuli, three have emerged as quite potent: hydrostatic pressure (10MPa at 0Hz during days 10-14), TGF-1 (30 ng/ml for 2 wks), and chondroitinase ABC (applied at 2 wks), applied in combination. Mechanisms linking these stimuli to the engineered tissues' biomechanical properties have also been elucidated to explain their synergisms and to consolidate them into simple culture protocols. A functionality index (FI) allowing the establishment of quantitative success criteria and validated for the comparison of constructs to native tissue showed that construct properties have attained FI values approaching 1, the value of native tissue. Based on these promising results and additional in vivo murine, leporine, and ovine data, this proposal will investigate the global hypothesis that constructs will show durability without an adverse host response via three aims: The objective of Aim 1 is to use a short-term (12wks), leporine patella resurfacing model to examine the hypotheses that: 1) not only will constructs retain stability and integrity in vivo, thir FI values will be improved by implantation, and 2) neither the allogeneic cells nor the culture products will elicit adverse host responses (local/systemic). Aim 2 employs the murine model to validate that implant scale-up would not alter neocartilage biomechanical properties. Aim 2 will also address certain challenges that are common across diverse cartilage regeneration strategies, namely initial fixation, subsequent integration, and durability against wear; these issues will be tackled using a chondroconductive glue, exogenous lysyl oxidase, and the chondrotuning method that yields robust and lubricious implants. Finally, Aim 3 will test the hypothesis that durable healing can be achieved for up to 12 months in an ovine model. This aim will also identify a minimum cell number that can be employed to achieve effective healing at 1 year. By following FDA's guidance document (Preparation of IDEs and INDs for products intended to repair or replace knee cartilage), and if the proposed study's hypotheses are proven, the results will provide exciting validation of the clinical translatability of self-assembed articular cartilage constructs.